The design of current third generation (3G), and enhanced 3G, wireless access networks is driven by the need for high speed internet access. Increasingly, consumers are moving to wireless communications for the delivery of services and applications using TCP/IP (Transmission Control Protocol/Internet Protocol). This trend is growing with the increase in internet-enabled wireless devices available to users, including cellular telephones, Personal Digital Assistants (PDAs), and other devices. The applications that are now available or contemplated for wireless devices include access to the World Wide Web, video telephony, voice over IP, e-mail, etc.
However, wireless networks, whether fixed or mobile, suffer certain disadvantages over their wired counterparts, particularly in the delivery of IP applications. This is mainly due to the significantly greater lost or dropped packets in wireless networks, as compared to wireline. Such losses can be largely attributed to the changeable quality of the channel over which IP packets are sent. For example, the wireless channel condition is highly dependent on the location of the wireless terminal in relation to its base station, and extraneous external or atmospheric interference. The combination of these factors can have a significant effect on the delivery of data services over wireless channels.
An automatic retransmission request (ARQ) scheme is generally implemented in a wireless access network to enable packets that have not been received at a receiver to be retransmitted. Current 3G wireless link ARQ schemes are NAK-based schemes with static retransmission parameters determined on a per connection, or burst, basis. Such systems include the cdma2000 1xRTT standard, the Universal Mobile Telecommunications System (UMTS), High Data Rate (HDR), and Enhanced Data Rates for GSM Evolution (EDGE). For example, a static ARQ may support two rounds of retransmissions, and two retransmissions in each round, to meet a desired packet loss rate for the link. Such a static ARQ scheme has two main disadvantages for supporting packet applications. First, resources can be wasted. For example, if the first retransmission in a round has been correctly received, the second retransmission is a waste of radio resources. Secondly, there is a possibility that the delay introduced by retransmission will be longer than the tolerable packet delay for a given packet. This results from the fact that a static ARQ processes all packets in the same way, regardless of per packet QoS. This can result in intolerable delay for certain packets. For example, if a packet's delay margin does not permit two rounds of retransmission, the above static ARQ does not support the required QoS for that packet.
Therefore, to better support high speed wireless internet access, it is desirable that the ARQ design should support per packet QoS, instead of using static parameters, where the per packet QoS is, for example, a function of each packet's delay bound. In this way, system resources can be more efficiently utilized as compared to systems using a static ARQ scheme, and system capacity can be increased as a result.